This application claims the benefit of Korean Application No. 2000-79012, filed on Dec. 20, 2000, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a disk-type recording medium, and more particularly to a disk-type recording medium capable of limiting breakage caused by a crack formed around a center hole of the disk-type recording medium.
2. Description of the Related Art
Recently, the use of disk-type recording media such as optical disks or magneto-optical disks have become common in optical or magnetic optical signal recording/reproducing methods. These disk-type recording media can be divided into three kinds of recording media: read only memory type recording media like compact disks; one-time recording type recording media, which allows a user to record data once; and over-writing recording media, like optical disks.
Referring to FIGS. 1A and 1B, a disk-type recording medium 1 includes an annular non-recording surface portion 1b formed around a center hole 1a and an annular information-recording surface portion 1c spreading around the non-recording surface portion 1b. To record and/or reproduce information in and/or from the disk-type recording medium 1, a user typically puts the disk-type recording medium 1 in a carrying device like a disk tray, to load the disk-type recording medium 1 in a disk player. Then, the center hole 1a of the disk-type recording medium 1 is loaded in a turntable 2 installed in the disk player, and the disk-type recording medium 1 is spun at a high speed by a spindle motor 3. During the high-speed spinning, a chucking unit prevents the disk-type recording medium 1 from being separated from the turntable 2. As described above, while the disk-type recording medium 1 is spun at high speed, information is recorded and/or reproduced in and/or from the information-recording surface portion 1c of the disk-type recording medium 1 by a recording/reproducing unit, such as an optical pickup device or an optical head.
Recently, the RPM (revolution per minute) of the spindle motor 3 has been increased due to the increase of information-recording density of the disk-type recording medium 1. Therefore, some problems regarding the high-speed spin of the disk-type recording medium 1 have been exposed. Among the problems, when the disk-type recording medium 1 is spun, due to its shearing, the disk-type recording medium 1 may break. Thus, with this increased spin speed, the sequential breakage of peripheral devices, like an optical pickup device, frequently happens. It is known that the breakage from shearing of the disk-type recording medium 1 is caused from a short length crack being formed around the center hole 1a of the disk-type recording medium 1, such as when a user unconsciously exerts a shock to the disk-type recording medium 1. If the crack is of a predetermined critical crack length, the internal stress on the disk-type recording medium 1, caused by a centrifugal force from the spin of the disk-type recording medium 1, transfers from the front end of the crack to the outer line of the disk-type recording medium 1, and finally causes the shearing of the disk-type recording medium 1. Moreover, a bending stress on the disk-type recording medium 1 by the centrifugal force is increased with the shearing of the disk-type recording medium 1, thereby causing the disk-type recording medium 1 to become deformed and distorted. Lastly, the crack also causes the chucking unit to become separated. Therefore, the separated chucking unit and the broken disk-type recording medium 1, due to the huge energy generated by the high-speed spin, collide with other peripheral devices of the disk player, causing critical damage to a product.
In addition, even though the crack may not fully reach the critical crack length, the possibility of fatigue fracture still remains.
To solve the above and other problems, it is an object of the present invention to provide a disk-type recording medium having an improved construction for hindering a crack generated in the disk-type recording medium from advancing to an outer edge of the disk-type recording medium.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above object and other objects, the disk-type recording medium may include an information recording surface portion disposed around a center hole and a crack hindering element hindering a crack generated around the center hole from advancing to an outer edge of the disk-type recording medium. The crack hindering element includes at least one annular protrusion portion around the center hole. In addition, the annular protrusion portion may have a bead shape, in a sectional view.
In addition, according to another aspect of the present invention, the disk-type recording medium of the present invention may include an information recording surface portion disposed around a center hole of the disk-type recording medium and a crack hindering element hindering a crack generated around the center hole from advancing to an outer edge of the disk-type recording medium. The crack hindering element may include at least one annular iron core embedded around the center hole.
Moreover, according to another aspect of the present invention, the disk-type recording medium of the present invention may include an information recording surface portion disposed around a center hole of the disk-type recording medium and a crack hindering element for hindering a crack generated around the center hole from advancing to an outer edge of the disk-type recording medium. The crack hindering element may include at least one annular taping member adhered to the area around the center hole, the annular taping member being made of a material different from a material of the information recording surface portion. The annular taping member may be made of a fiber material.
Additionally, according to another aspect of the present invention, the disk-type recording medium of the present invention may include an information recording surface portion disposed around a center hole of the disk-type recording medium and a crack hindering element for hindering a crack generated around the center hole from advancing to an outer edge of the disk-type recording medium. The crack hindering element may include a coating layer, with the coating layer being made of a certain material and disposed on an area around the center hole hindering a crack from generating. The coating layer may be made of a viscoelastic material.
Moreover, according to another aspect of the present invention, the disk-type recording medium of the present invention may include an information recording surface portion disposed around a center hole of the disk-type recording medium and a crack hindering element hindering a crack generated around the center hole from advancing to an outer edge of the disk-type recording medium. The crack hindering element may include an annular flange portion disposed around the center hole, the annular flange portion being thicker than the information recording surface portion.